The flame treatment of metallurgical intermediates, sulfidic ores and/or sulfur-containing ore concentrates in the presence of oxygen-containing gases and at roasting or higher temperatures is a well known expedient to recover a residue or metallurgical product having a reduced sulfur content by, in part, the transformation of the sulfur originally contained in the metallurgical material into sulfur dioxide.
When the treatment is carried at high flame temperatures, e.g. of at least 1500.degree. C., the product or residue can be recovered in a molten phase and practically all of the sulfur is discharged in the form of sulfur dioxide.
These processes are not generally autogenous and thus may require the supply of fuel to the system. The process can be carried out in reverberatory hearth furnaces, short-drum furnaces and rotary kilns or drum furnaces.
Of particular interest as to such flame treatments are flash or suspension smelting or reverberatory-furnace smelting of the raw material which can be enriched in ore and to which fluxes can be added. These systems make use of fuels and produce a "concentrate", e.g. a copper matte, containing various levels of nickel, zinc and lead sulfide depending upon the source of the feed, i.e. the starting metallurgical material (see Meyers Lexikon der Technik und der exakten Naturwissenschaften, Bibliographisches Institut, Mannheim, Germany; Wien, Austria; Zurich, Switzerland; Vol. 3, p. 2308; Winnaker and Kuchler, Chemische Technologie, Vol. 6, pp. 228/229, Carl Hanser Verlag, Munchen, Germany 1973.)
A disadvantage of these processes, however, is that without the added fuel in considerable quantities the desired or necessary reaction temperatures cannot always be attained or sustained, the quantity of fuel which is necessary being dependent upon the nature of the feed. Consequently the process cannot always be carried out economically.